This invention lies in the field of electronic and mechanical devices having a number of keys which perform the function of reading-in data for the device. More particularly the invention lies in the field of electronic calculators, especially the portable and hand-held type, and like devices wherein in the prior art a plurality of depressible keys are used to feed data to the electronic device.
Many electronic devices are on the market today which perform mathematical or algorithm functions. Such devices are usually provided with a plurality of keys which are depressed by the user to read in or stimulate a desired variable. Examples of this can be seen in hand-held calculators which may have as many as 30 different keys. Each of these keys is depressable and reads in one particular data into the calculator. Furthermore, since the hand-held calculators are small and portable, it is generally necessary that the keys be very small and minute. The problem with such small keys is that it requires a gread deal of concentration on part of the user to appropriately position his finger whilst depressing the desired key. This, of course, is distracting and requires the user to spend a good deal of time in proper selection of the keys, which time is necessarily a diversion from other functions that the mental process could be utilized for. Some manufactures of minute or mini-calculators, for example calculators which are of the size of a wrist watch, have provided a small toothpick-like rod by which the user depresses the appropriate key.
Besides the problem of the size of the keys, having plurality of keys, one for each variable requires the training of the users' fingers in an unproductive manner. For example, the common ten-key adding machine or calculator utilized in many offices requires that the user train at least three and usually four of his fingers which then become occupied in feeding figures 0 to 9 into the machine. However, a great deal of time is spent by the user to properly train his fingers, much like a typist has to practice typing for a long time before he or she can achieve mastery of using the typewriter. Furthermore, such ten-key adding machine or calculators generally have the keys positioned in close proximity of one other and as such, many times one finger may accidentally slip from one key onto another. To avoid such problems it is generally required that the ten-key calculator have large keys, which accordingly take up large space making the device bulky. Additionally, large keys add to the cost of the particular device.
It is well-known that human fingers can be trained so that they can use some of the devices on the market without really looking at the machines, as noted in the ten-key adding machine described above. This, of course, is impossible in a case of small hand-held calculators due to the spacing of the close keys and their relatively small, sometime minute, sizes.